Devices for transmitting a force are known, for example, in the form of carrying handles or as chains formed from chain links. A plurality of such devices are used, for example, for carrying large loads. In the following description, reference is made predominantly to loops for the transmitting of a force. This is purely for the simplification of the description and is not to be regarded as restrictive. All embodiments can be transferred in a corresponding manner to chain links.
Carrying handles (simplified as loops) consist as a rule of two semicircular segments, referred to as the loop heads, and straight sections located in between. If the loop is formed from a composite material, such as (Kevlar) fibers impregnated with resin, the dimensionally-stable loops can be formed as one piece, without “seam points”. Dimensionally-stable means that the loops exhibit the collective form described heretofore without loading and regardless of their orientation (relative to the ground). The application and exertion of force is effected by means of bolt-like structural elements, which have an outer contour adapted to the semicircular form of the loop heads and are arranged inside the loop heads, such that the structural elements specifically do not come in contact with the straight sections. By means of the structural elements, a radial pressure is introduced into the loop heads. The radial pressure exerted by the structural elements is converted in the loop heads into tensile forces in the direction of the fibers. A force transmission between the two loop heads in the straight regions is effected by a tensile loading in the direction of the fibers of the loop.
The axial tensile force, i.e. the tensile force in the direction of the fibers, and the radial pressure, i.e. the force effect perpendicular to the direction of the fibers, has the effect of a mixed loading in the loop heads. On the one hand, this limits the maximum force which can be transmitted by a loop, which, with loops made of a fiber composite material, is defined by the maximum pressure loadability of the material perpendicular to the direction of the fibers. On the other hand, the mixed loading leads to a substantial magnification of the material stresses in the region of the transition from the loop head to the straight sections. What is referred to as the tension magnification has the known effect of causing the loops to fail in the region of the transition points. The transition points therefore limit the maximum carrying capacity of the loop. This has the effect of an only partial utilization of the strength of the material in the other regions, since, in particular with loops made of fiber composite material, the fibers should be circumferential and, on the other hand, the weakest point determines the necessary geometry and therefore the necessary use of material.
FIG. 1 shows in a diagrammatic representation the structure of a typical known loop, as has been described heretofore. The device 10 formed as a loop for transmitting force comprises two curved arch segments 11, 12 lying opposite each other. The arch segments 11, 12 are connected to each other by two straight limbs 13, 14 of length L, which are equally long. The reference numbers 15, 16, 17, 18 identify the transition points. Depending on the material used for the loops, the arch segments 11, 12 could be connected to the limbs 13, 14 in the region of the transition points by mechanical means, for example by material bonding. If the loop is formed from a fiber composite material, then the curved arch segments 11, 12 and the straight limbs are produced continuously from one material at the transition points 15, 16, 17, 18, i.e. resin-impregnated fibers. The transition points 15, 16, 17, 18 therefore represent regions of the loops relevant only for the adhesion of the arch segments 11, 12 to the straight limbs 13, 14.
The force application and exertion is effected by means of two bolt-like structural elements 19, 20 represented in cross-section. Since the arch segments 11, 12 exhibit the form of a semicircle, the outer contour 21, 22 of the structural elements 19, 20 is likewise formed as semicircular, such that the outer contour 21, 22 comes fully in contact with the arch segments 21, 22. The outer contour 21, 22 of the structural elements 19, 20 is therefore of such a nature that they directly adjoin the transition points 15 and 18 and, respectively, 16 and 17, but specifically do not exhibit any contact with the straight limbs 13, 14. As a result, a defined force application and exertion is guaranteed. Shown in the drawing is only the region of the force application elements which is relevant for the application of the force. The bolts may of course also extend into the region of the straight segments 13 and 14.
The length L of the limbs 13, 14 can in principle be selected at will. Reference character R identifies a radius of the arch segments 11, 12. In the diagrammatic representation, the radius of the two arch segments 11, 12 is identical. In practice, the radii of the arch segments could also be different, wherein the arch segment with the smaller radius then determines the load capacity. The arch segments 11, 12 and the limbs 13, 14 exhibit an identical thickness D over the entire course.
In the case of loops made of a fiber composite material, the mixed loading of axial tensile force and radial pressure are matched inasmuch as the loops are dimensioned according to the force which is required to be transmitted and the permissible tensions, taking into account the points of maximum loadings. This leads to the situation, however, that the loop geometry, i.e. the thickness D of the sections of the loop and the radius R of the arch segments, are subject to severe restrictions. Such a loop geometry may, however, run counter to applications in which loops subject to high loading must be used. This is the case, for example, with the suspension of a superconducting exciter winding of an HTS generator with hot pole core by means of a plurality of loops. Since in this application the loops cause an undesirable conductance of heat, it would in fact be purposeful for the thickness D (generally the cross-section) of the loop sections to be kept as low as possible. In order to be able to configure the tension magnification at the transition points as fail-safe as possible, however, the loop cross-section must be selected as considerably greater than is necessary for transmitting the forces in the straight section. In order to compensate for the increase in heat ingress in the cold part which is caused by this, the length L of the straight limbs of the loop must in turn be increased accordingly. For geometric and electromagnetic reasons, this in turn is in part not possible, and at least not desirable.